Question Author
Sorry folks, perhaps I didn't make myself clear. The black coating that comes off all over my fingers and sponge is from the underside of the grill plates not the, upper, non-stick surface. I like all of you, only use a plain sponge to clean the upper surface of the grill plates.
The George Foreman model I have, does have removable grill plates. The previous one I had had fixed plates.
The instructions of the grill do indeed say that that the removable plates can be put into a dishwasher.